The UFC 158 card in Montreal has taken on a whole new dimension after president Dana White said March 16 would play host to a welterweight tournament.

Georges St-Pierre defends his 170lb title against Nick Diaz in the night's main event, but underneath that bout are two hugely significant welterweight contests.

Carlos Condit rematches Rory MacDonald, while Johny Hendricks takes on Jake Ellenberger, and White confirmed at Wednesday's press conference that it is a tournament, meaning the winners could meet each other later in the year.

"This is a six-man tournament," White told the media.

However, he did later muddy the waters on the situation, saying: "I would have to say the Johny Hendricks thing, if Johny Hendricks looks good and wins his fight, it [the next title shot] will probably be Hendricks. But then again who knows, we'll see what happens that night."

The news raises a question mark over the 2013 plans of St-Pierre, who had been expected to fight Hendricks after Diaz - if Hendricks beat Ellenberger. The announcement of a tournament would leave GSP without a challenger to his crown post-Diaz.

One theory may be that the UFC is clearing the way for a St-Pierre v Anderson Silva superfight, after Michael Bisping's defeat to Vitor Belfort left Silva without rival at 185lbs.

White did not go into the details of St-Pierre's future, preferring instead to focus on the long-awaited battle of GSP and Diaz, whose previously scheduled clash was cancelled.